The present invention relates generally to guitars and in particular to a guitar that can be played without fretting through the use of servo controlled string tension.
The guitar is an extremely versatile musical instrument, in part because it offers the performer an ability to independently and flexibly control four musical parameters of: note pitch, note volume, note timing, and note overtones (timbre) in a melodic polyphony. In contrast, instruments like the piano, which rival the guitar for popularity, provide a far more constrained control of pitch (only to semitones) and volume, and very little control of note overtones. Skilled guitarists can exploit various modulation and transition effects such as glissando, vibrato, “hammer-on”, chiming, pitch bending, and other techniques to offer additional variation to the audio palette provided by the instrument. The introduction of the electric guitar in the 1930s further expanded the variety of sounds that can be produced by this instrument.
Unlike other polyphonic instruments such as the harp and piano, the guitar divides the task of controlling note pitch and the tasks of controlling note volume and timing between the two hands of the performer. The control of note frequency is simplified by the use of a fretboard allowing one-handed selection of multiple string lengths (and hence note pitches) within a given overall tuning of the strings. Yet despite the simplicity of the guitar fretboard, this approach to pitch control of polyphonic notes has some significant disadvantage. First, given a particular string tuning, it can be difficult or impossible to play some chords or change between certain chords smoothly. Second, the raised frets of the fretboard, which simplify the process of changing the string length to obtain a precise pitch, interfere with some modulation and transition effects possible on the guitar, such as glissando or vibrato.
Often it is desired to further modify the sound of the guitar string, for example, using “effects” boxes such as compressors (sustained), clippers (fuzz) and sweeping filters (wah). Desirably these effects may be controlled during guitar playing; however, such control must normally be relegated to the player's foot to the use of a “pedal” making it difficult to achieve precise control and necessarily tying the musician to a fixed location which may not be desirable for stage performance.